Recently, a batch type is generally adopted instead of a single type in a semiconductor cleaning process. The single type, which uses a method of processing a sheet after another of wafer, has a lot of advantages in comparison with the batch type. That is, since new chemical can be supplied every process and there is no influence by other wafers, it is possible to solve the problem of particles reattachment. In addition, since the wafer performs a rinse process while rotating without moving after the chemical process, the chemical liquid is well replaced.
The cleaning process of the single type requires a small area in installing equipments, has a fast process speed, perform uniform etching, and has improved responding performance in process. However, it has a disadvantage in productivity and consumption of chemical since a sheet after another is processed.
Buffered Oxide Etchant (BOE) is known as a representative conventional wet etchant for removing silicon dioxide. The conventional BOE is an etchant containing ammonium fluoride (NH4F) and hydrogen fluoride (HF) as a fluorine compound and having selectivity of silicon dioxide (TEOS) to the silicon nitride film of 50 or higher, preferably 140.
The conventional BOE using ammonium fluoride (NH4F) and hydrogen fluoride (HF) as the fluorine compound controls a content by increasing the content of hydrogen fluoride (HF) or ammonium fluoride (NH4F). However, increasing a weight ratio of hydrogen fluoride (HF) and ammonium fluoride (NH4F) causes a problem of Solid Phase Segregation of ammonium fluoride (NH4F). The problem of Solid Phase Segregation of BOE occurs when the concentration of hydrogen fluoride and ammonium fluoride is increasing. Solid Phase Segregation may occur at 20° C. or higher when the temperature of Solid Phase Segregation is high. Since Solid Phase Segregation occurring at 20° C. or higher causes a problem in a process temperature, transport and storage, there are many difficulties in usage. There is also a problem that Solid Phase Segregation of ammonium fluoride (NH4F) in a spray nozzle due to a sublimation property of ammonium fluoride (NH4F) may contaminate particles.
Therefore, a composition for wet etching that selectively removes silicon dioxide for a short time at a high etch rate on silicon dioxide and a low etch rate on the silicon nitride film existing on a substrate in a process of preparing a semiconductor is required to apply the conventional BOE to the wet etching process.